Printed Circuit Board Coils of Multitrack Litz Structure for 3.3-kW Inductive Power Transfer System

This article presents the optimization procedure of an inductive power transmission (IPT) system, which utilizes large size spiral printed circuit board (PCB) coils for high-power transfer. PCBs for coil assembly provide advantages in the manufacturing process through the use of cost-effective flexible fabrication techniques. Furthermore, this kind of construction offers a low-profile device, which is of great interest for applications with space constraints. PCB-based IPT system coils can achieve high energy efficiency by applying Litz-structure braiding techniques, as investigated in this work, where the objective was to obtain an optimized balance between the conduction losses and the proximity losses associated with the number and dimensions of the traces. Considering the geometrical dimensions and manufacturing constraints, we will proceed to obtain the characteristics of the coil to achieve optimal performance. The estimation of coil losses was in part based on finite-element simulations, and the results were conveniently processed with the appropriate mathematical methods. Numerical simulation and experimental results were conducted for validation on a prototype suitable to transfer up to 3.3 kW for a transmitter (TX)–receiver (RX) distance of 10 cm. In the experimental arrangement, a maximum efficiency in the coils of 93% has been measured, and the overall efficiency of 88% has been reached for the entire IPT system.